With the proliferation of selective call services, many users of selective call receivers typically receive messages on more than one service. For example, a user could subscribe to a wide area network system and at least one on-site network system. Wide area network systems typically allow for reception of selective call messages over a large area such as an urban area, or even statewide. On-site selective call network systems have a localized coverage area, some solely within one building. Each selective call network system (e.g., paging systems) is assigned a unique frequency in a manner such that systems proximately located to each other will operate on distinct and separate selective call communications paths or frequencies called channels.
It is desirable that the reception of a message by a selective call receiver (e.g., a pager) have a high probability of reception. To insure a high probability of selective call message reception, a message is typically transmitted by a wide area network selective call system having an associated coverage area wherein a selective call receiver user is normally found.
If a selective call message is being transmitted for the user by a wide area network system and the user is in a building, there can be difficulty in reception because of the interference of the surrounding building. For example, a doctor on staff at one or more hospitals within an urban area and residing within that urban area typically receives messages on a wide area selective call network system and one or more on-site selective call network systems operated by the hospitals. If the doctor is inside a hospital and the selective call receiver is tuned to the on-site selective call system frequency, he cannot receive transmissions from the surrounding wide area network system. To increase the probability of message reception, the doctor may use two pagers: one for the wide area network and one for the on-site network. The doctor's selective call receiver may also scan between the wide area and on-site channels to increase the probability of message reception. An example of two channel scanning is described in U.S. Pat. No. 4,644,347 assigned to the assignee of the present invention. While a selective call message is being received on one channel, though, the other channels are not scanned. A message transmitted for a user on one frequency, therefore, could not be received by the user if he is receiving a message concurrently on another frequency.
Thus, what is needed is a system for increased reliability of selective call message reception in a wide area selective call network system even if the user is in a location which interfers with signal reception or is receiving messages from an on-site selective call network system.